1. Field of the Invention
The present invention relates to a portable timepiece that includes a push button.
2. Description of the Related Art
In portable timepieces such as a wristwatch or a pocket watch, there is a portable timepiece that includes a push button which operates a contact of a module built in a timepiece exterior assembly. The push button is pushed, whereby, for example, in a quartz type portable timepiece, a timepiece display can be switched from an analog display to a digital display, and it is possible to switch a date and a day of week digitally displayed.
In the related art, in this kind of portable timepiece, the push button is constituted by an integral structure that is formed by a shaft portion and a head portion having a diameter greater than that of the shaft portion and provided integrally with the shaft portion, and is attached to a body of the timepiece exterior assembly by a configuration as below.
That is, the shaft portion of the push button with a water-proof packing attached to an outer peripheral portion thereof is penetrated through a pipe attached to a through hole of the body from outside the body, whereby a snap ring is attached to a shaft end portion of the push button protruded inside the body, by interposing a coils spring between a body outer end portion of the pipe and the head portion of the push button in a compressed state, the snap ring having a diameter larger than an inner diameter of the pipe is engaged with an inner end of the pipe protruded inside the body, and the push button is attached so as not to fall out to the outside of the body (see JP-A-2003-7164 (Patent Document 1)).
In the related art, since the snap ring is used so as to stop a push button formed of an integral structure to a body, an annular snap ring attachment groove is formed in a part to which the snap ring is attached in the shaft portion of the push button. As a result, strength of a thinned part is the lowest in the shaft portion of the push button.
For this reason, when a portable timepiece falls down, there is a concern that the shaft portion may be bent from the snap ring attachment groove by impact to be applied to the push button accordingly. Particularly, since a length from a tip of the shaft portion close to the contact of the movement to the snap ring attachment groove is long to the extent of a model that has a small movement and a large diameter of an hour plate, there is an increasing possibility that the shaft portion is bent. When the shaft portion is bent in this manner, even if the push button is pushed, a malfunction (hereinafter, referred to as a contact malfunction) may be caused in which the contact is not properly pushed.
Furthermore, since the snap ring is very small, the handling thereof is difficult when the same is attached to or detached from the shaft portion of the push button. In addition to this, in order to attach the snap ring to the shaft portion of the push button, there is a need to perform a work in a limited narrow space of an inner side of the body in the state in which the shaft portion is penetrated through the pipe. Thus, the attachment workability of the snap ring is bad, and by the same reason, workability of removing the snap ring from the shaft portion of the push button is also bad. In addition, when attaching and detaching the snap ring to and from the shaft portion of the push button, there is a high possibility that the snap ring, which is a small part, is lost.
In this manner, in the portable timepiece with the push button of the related art, there is a problem in that the shaft portion of the push button attached to the body is likely to be deformed by the impact, and the attachment and detachment workability of the push button to the body is bad.